Certain molecules, such as carbon dioxide or water, may be targeted and collected from gas streams for a variety of applications. For example, carbon dioxide may be collected as a byproduct of industrial processes and to remove excess carbon dioxide from a supply of air.
Carbon dioxide may be obtained from various sources using various techniques. Traditional carbon dioxide collection techniques may be very energy intensive, particularly when run on an industrial scale. The two most demanding energy requirements for carbon dioxide collection are typically the energy required to drive a gas stream past or through a collecting medium and the energy required to regenerate and capture the carbon dioxide from the collecting medium. Therefore, carbon dioxide material costs may become significant, particularly when large quantities are used.
One method for collecting carbon dioxide employs a molecular sieve to adsorb the carbon dioxide molecules. Removal of the adsorbed carbon dioxide requires a significant amount of energy. Such energy is usually supplied by radiant heating and/or by pulling the molecules off using a high vacuum.
However, heating the system requires significant energy and, therefore, is inefficient. It also requires the structural components of the system be designed such that all the component parts can rapidly and efficiently radiate heat evenly throughout the system. This usually requires a metallic system, a plurality of radiant heaters, and a supply of electrical power. Additionally, since most molecular sieves are made from ceramic materials, which are normal insulators, they do not conduct heat easily and must be designed in close proximity to multiple heat sources.
Further, since molecular sieves are also porous materials that have polar charges, they also have an affinity to hold other charged molecules. This can make the molecular sieve less likely to release charged molecules, such as water. Therefore, certain target molecules may require even higher temperatures to be released, thus requiring more energy.
An additional energy source, such as a high vacuum, may also be required to effectively release the molecules. Utilization of a vacuum adds additional costs to the system by requiring additional energy for operation and additional structural components. The molecular sieve must be housed in a chamber that is capable of withstanding lower pressures, thus the chamber must be reinforced and vacuum valves and seals must be added.
Known carbon dioxide collection systems commonly operate by passing a gas stream through a collection bed to adsorb the carbon dioxide from the gas stream. The carbon dioxide would then have to be recovered, or desorbed, from the collection bed by heat, vacuum, or a combination of the two. This would have to be accomplished within a chamber that is capable of sustaining a vacuum. Thus a thick, heavy walled chamber, usually made of metal, that is capable of withstanding thermal exposure and high vacuum without distortion is required. After a period of time, the adsorbed carbon dioxide is released into the chamber. The time period required is dependent on various factors, such as on the gas adsorbed and the conditions used to release the molecules. For example, the higher the temperature the faster the time, but more energy input is required at a higher operational cost. As another example, the lower the vacuum the faster the time, but more energy input is required at a higher operational cost and at a higher cost for the vacuum chamber and associated vacuum components.
According, those skilled in the art continue with research and development efforts in the field of carbon dioxide collection.